Double-walled container



Sept. 12, 1967 A. BARTHEL DOUBLE-WALLED CONTAINER 6 Sheets-Sheet 1 FiledSept. 12, 1963 INVENTOR. AL FKED 8/9,? 79 54 A mm. y

Sept. 12, 1967 A. BARTHEL 3,341,052

DOUBLE-WALLED CONTAINER Filed Sept. 12, 1963 6 Sheets-Sheet 2 INVENTORALFf'D BART/45 czm A770f/ EY Sept. 12, 19 67 I A, BARTHEL 3,341,052

DOUBLE-WALLED CONTA INER Filed Sept. 12. 1963 6 Sheets-Sheet 5 FIG. 3

/ INVENTOR ALF/( 50 5/22 7,451

A Tram/5y Sept. 12, 1967 A. BARTHEL 3,341,052

DOUBLE-WALLED CONTAINER Filed Sept. 12, 1963 6 Sheets-Sheet 4.

INVENTOR. ALFfiED BAETA 'L yv u fw ATTORNEY A. BARTHEL DOUBLE-WALLEDCONTAINER Sept. 12, 1967 6 Sheets-Sheet 5 Filed Sept. 12, 1963 INVENTORAlf/E50 8/9,? 77/54 )ww 6'. km

6 Sheets-Sheet 6 Filed Sept. 12, 1963 INVENTOR.

W Ci %2 ATTOE/I/EV United States Patent 3,341,052 DOUBLE-WALLEDCONTAINER Alfred Barthel, Indianapolis, Ind., assignor to Union CarbideCorporation, a corporation of New York Filed Sept. 12, 1963, Ser. No.308,541 5 Claims. (Cl. 220-44) This invention relates to an improveddouble-walled liquefied gas container for storing and transporting lowboiling liquids as, for example, liquid helium, hydrogen and oxygen.

In copending application Serial No. 198,987, filed May 31, 1962, to JohnA. Paivanas et al., now Patent No. 3,133,422, there is described andclaimed an improved low boiling liquefied gas container comprising aninner vessel for holding the liquefied gas and an outer shellsurrounding the inner vessel and spaced therefrom so as to form anintervening vacuum space with a temperature gradient thereacross. Anevaporation gas conduit is provided between the inner vessel and theouter shell for transporting such gas from the container. A compositemulti-layered insulation is disposed within the vacuum space andcomprises low conductive material and radiant heat barrier material, thelayers being disposed generally parallel to the container walls andnormal to the flow of heat. Multiple parallel spaced highly conductivemetal shields are also disposed in the vacuum space in heat exchangerelation with insulation. These shields are respectively joined by lowthermal resistance means to the evaporation conduit at regions where thetemperature, when the container is filled with low boiling liquefiedgas, is lower than the temperature assumed by the individual shieldabsent the joining.

The refrigeration of the evaporating liquefied gas discharging from theinner vessel is transferred to the conduit walls and thence through thelow thermal resistance means to the conductive shields. Stated inanother way, of the total heat entering a conductive shield from theatmosphere through the outer shell and the contiguously associatedinsulation, a portion is intercepted and conducted to the dischargingevaporation vapor. Only the remainder of the total heat is allowed topass further towards the cold inner vessel. Thus, with a succession ofsuch interceptions (i.e. multiple conductive shields), the net heatinflux to the cold inner vessel is greatly reduced.

Although the conductive metal shields have been found highly effectivein improving the thermal performance of the composite multi-layerinsulation, their juncture with the evaporation conduit has introducedsubstantial problems. For example, the inner vessel is preferablywrapped mechanically with the composite multi-layered insulation and thewrapping sequence must be suspended each time a metal shield is to beintroduced and joined to the evaporation gas conduit. One suitablejuncture means is a metal disk fitting concentrically around theevaporation conduit. The disks must be spaced longitudinally along theconduit and heat bonded thereto, as by silver soldering. This means thatif ten thermal shields are to be employed within the insulation, thewrapping operation must be interrupted ten times. Such an assemblyprocedure greatly increases the labor costs of construction andconsequently the overall cost of the container. While the improvement inthermal insulating quality resulting from the multiple conductiveshields more than justifies the additional cost in the case of extremelyvaluable and cold liquids such as liquid helium and hydrogen, theperformance improvement does not justify the use of metal bonded disksand shields in the construction of doublewalled containers for lessvaluable liquefield gases as, for example, liquid oxygen and nitrogen.

Another limitation of the disk-type construction is the difficultyencountered in establishing and maintaining a thermal associationbetween the disks-and the radiation heat barrier component of thecomposite layered insulation and/or the conductive shields. Either orboth the radiation heat barriers and the conductive shields may be inthe form of metal foil strips or ribbons, and they tend to tear whenpressed against the sharp edges of the disk during the wrappingoperation. If the foil is completely severed, the heat transfer pathbetween the evaporation conduit walls and the insulation is eliminatedand the shields become ineflective.

It is an object of this invention to provide an improved double-walledliquefied gas container having composite multi-layered insulation, andconductive metal shields in the intervening evacuable space.

Another object is to provide such a container that does not require ametal bond to thermally join the conductive metal shields to theevaporation gas conduit.

A further object is to provide an improved, less time consuming andtedious method for assembling the container, which method avoids thetendency to sever the radiation heat barrier and/or the conductiveshields.

Other objects and advantages of this invention will be apparent from theensuing disclosure and the appended claims.

In the drawings:

FIG. 1 is a view of a longitudinal cross-section through a liquefied gasstorage container illustrating one embodiment of the invention;

FIG. 2 is an isometric view looking downwardly on a frusto-conicalsection suitable for use in the FIG. 1 container;

FIG. 3 is an isometric view looking downwardly on an alternativefrusto-conical section suitable for use in the FIG. 1 container;

FIG. 4 is an isometric view looking downwardly on the FIG. 3frusto-conical section clamped around the evaporation gas conduit;

FIG. 5 is an isometric view looking downwardly on a compositemulti-layered thermal insulation suitable for use in the FIG. 1container;

FIG. 6 is a longitudinal elevation view of apparatus suitable fororbital wrapping the FIG. 5 multilayered insulation around the FIG. 1container;

FIG. 7 is an isometric view looking downwardly on a frusto-conicalsection-conductive shield assembly suitable for use in the FIG. 1container; and

FIG. 8 is a view of a longitudinal cross-section through a liquefied gasstorage container illustrating another embodiment of the invention.

One embodiment of this invention takes the form of a-double-walledcontainer comprising an inner storage vessel and an outer shell beingarranged and constructed with a vacuum space therebetween. Anevaporation gas conduit is provided between the inner vessel and outershell for transporting evaporated liquefied gas from the container theconduit having a temperature gradient across the vacuu'm space. Acomposite multi-layer insulation is disposed within the space andcomprises low conductive material and radiant heat barrier material. Atleast one and preferably multiple highly conductive metal shields aredisposed in the vacuum space and surround the inner vessel. The

conductive shields are also contiguously associated on both sides withthe composite insulation.

At least one frusto-conical section formed of heat c0nductive metal isconcentrically aligned around the evaporation gas conduit within thevacuum space and positioned with its small end frictionally bearingagainst the outer surface of the conduit for thermal contacttherebetween, one edge of the conductive shield contiguously contactingthe large end of the frusto-conical section. This shield edge and thefrusto-conical section large end, as well as the section small end andevaporation gas conduit are aligned with respect to the vacuum spacewidth and thermally contacted so that the shield edge and frusto-conicalsection are at temperatures lower than they would assume absent thethermal contacts.

In this manner, the refrigeration of the evaporation gas emerging fromthe inner vessel through the evaporation gas conduit is transferredconsecutively through the conduit walls, the frusto-conical section andthe heat conductive shield to the composite layered insulation. Statedin another manner, the heat inleak to the insulation is transferredconsecutively through the shield, frustoconical section, and conduitwalls to the emerging evaporation gas.

In a preferred embodiment, a multiplicity of highly conductive metalshields are positioned in parallel spaced relationship across the widithof the vacuum space and a multiplicity of frusto-conical sections arealso positioned in parallel spaced relationship across the vacuum spacewidth. The previously mentioned one edge of consecutive conductive metalshields contiguously thermally contacts the large end of consecutivefrusto-conical sections with the coldest metal shield edge contactingthe coldest section large end and the warmest metal shield edgecontacting the warmest section large end.

As used herein, the expression frusto-conical section refers to ageneral shape which is substantially the frustrum of a right circularcone, the latter being a solid generated by the rotation of a righttriangle about one of its legs as the axis. For the purposes of thisinvention, the cross-section of this section may depart slightly from atrue circle.

As previously indicated, the composite multi-layered insulation disposedbetween the warm and cold walls comprises low conductive material andradiant heat barrier material, thereby substantially reducing the amountof heat inleak due to conduction and radiation. The low conductivematerial is preferably fibrous and composed of many elements of smallcross-sectional dimension having a solid volume not exceeding percent ofits gross volume (at least 90 percent voids). A particularly suitablecomposite insulation consists of alternating layers of a thin flexiblemetal foil such as aluminum or copper of less than about 0.0008 inchthick and usually about 0.00025 inch thick, and an elasticallycompressible web or mat of glass fiber. This insulation is described andclaimed in U.S. Patent No. 3,009,601 issued Nov. 21, 1961 to L. C.Matsch, the disclosure being incorporated herein to the extentpertinent. Another widely employed low conductive material ispermanently precompacted paper composed of unbonded fibers, as morefully described and claimed in U.S. Patent No. 2,009,600 also issuedNov. 21, 1961 to L. C. Matsch.

Another suitable composite multi-layer insulation is the metal-coated,flexible plastic material described in U.S. Patent No. 3,018,016 issuedIan. 23, 1962 to M. P. Hnilicka, Jr. The metal coating should have athickness less than about 0.25 micron and yet be sufficiently thick tohave an emissivity less than 0.06. The individual layers of metal-coatedplastic are preferably permanently deformed, as by crumpling, so as tobe free of extensive areas of planar contact. A suggested composite isaluminum-coated polyethylene terephthalate film. Another satisfactorymetal-coated substrate is thin metallized paper such as metallizedglassine.

Still another composite multi-layered insulation for use in the vacuumspace consists of the paper layers and finelydivided radiant heatreflecting bodies of less than about 500 microns in size, beingincorporated in and uniformly dispersed through the layers, as well as abinder for cementing the heat reflecting bodies to the fibers. The

finely-divided radiant heat reflecting bodies may, for example, forformed of aluminum, copper, nickel and molybdenum. Best result-s areobtained when the radiant heat reflecting bodies are relatively small,with particle sizes of less than 50 microns as the major dimension.Aluminum and copper paint pigment flakes of less than 0.5 micronthickness are especially suitable. The fibers may, for example, beformed of glass, ceramic, quartz, or potassium titanate. When glassfibers are used, they are preferably of less than 5 microns diameter,while a fiber diameter range of 0.2 to 3.8 microns gives best results.The reflecting body-containing paper may, for example, be formed onstandard paper-making machines using colloidal silica as a binder.

The highly conductive metal shields may, for example, be thin, flexibleand light in weight, and thus essentially self-conforming to the contourof the composite insulation layers, e.g. 0.001-0030 inch thick. Shieldsof such thinness, however, are limited in the quantity of conductiveheat they can transport along their length to the area of contact withthe frusto-conical sections. The heat load or duty imposed on such thinshields must be kept low, and this is accomplished by employing thehighly effective composite multi-layered insulation on the warm side ofthe shield.

While each conductive shield may be a single thickness of metal, it maybe alternatively applied as a multiple thickness of very thin foil by,for example, spiral winding such foil around the multi-layer compositeinsulation at the appropriate locations. Spiral winding is aparticularly advantageous technique for obtaining maximum flexibilitywith very low temperature gradient along the shield. The total thicknessof each conductive shield is related to its thermal conductivity and thelength through which heat is conducted. The total thickness, whilerelatively thin and non-sel-f-supporting as previously discussed, mustbe sufficient to limit the maximum temperature difference across theconductive shield to a low value which is less than the temperaturedifference between immediately adjacent shields at a particularcross-sectional plane through the insulation construction.

It is important to clearly differentiate the heat conductive shields ofthis invention from radiation shields, employed by certain prior artinsulations. The conductive shields are formed of highly conductivematerial having a thermal conductivity k of at least 5 B.t.u./hr.-ft. R.at K. and preferably 40-400 B.t.u./hr.-ft. R. Lower values do not permitsufliciently rapid heat transfer to the cold evaporation gas as it flowsthrough the conduit between the cold inner vessel and the relativelywarm outer casing. Also, such heat conductive shields need not be highlyreflective. Suitable heat conductive shield materials include aluminum,copper, silver and gold. In contrast, the prior art radiation shieldsneed not be highly conductive and, if desired, may be composed ofmetalcoated plastic films, most plastics having relatively low thermalconductivity values.

The heat conductive metal shields may alternatively be sufficientlythick to be substantially rigid so as to support its own weight, thatis, for example, -inch aluminum sheeting. Whether the conductive shieldsbe relatively thin and non-self-supporting or sufliciently thick tosupport their own weight, it is necessary that they be contiguouslyassociated with and in thermal association to the insulation foreffective cooling. This may be accomplished during assembly by wrappingcomposite insulation layers between adjacent shields. Alternatively, theshields may be thermally bonded to the radiation barrier sheet componentof the composite insulation.

The frusto-conical section is also formed of highly conductive but notnecessarily highly reflective metal as, for example, the same materialused for the conductive shields. This section must be of suflicientthickness, on one hand, to retain its substantially conical shape whenso formed, and is characterized by a resilient or spring -action whichprovides sufficient frictional bearing or grip against the outer wall ofthe evaporation gas conduit to insure a good mechanical and thermalcontact. On the other hand, the frusto-conical section must not be sothick as to prevent easy shaping and preclude this desired spring actionwhich permits the frictional and thermal contact against the conduitwall. The frustoconical section is preferably between 0.02 and 0.04 inchthick. A particularly suitable and inexpensive material was found to bel -inch thick aluminum sheeting for the 25-liter capacity vessel.

It has been indicated that one edge of the conductive shield mustcontiguously contact the large end of the frusto-conical section. Thisis necessary to insure a continuous path for heat transfer by solidconduction to the evaporation conduit from the composite insulation.Such contact may be achieved by simply extending the shield edge overthe frusto-conical section in an overlapping relation during assembly. Asatisfactory contact results by virtue of the compressive effectinherent in most wrapping techniques. If a more positive physicalcontact is necessary or desirable in a particular construction, a simplecompression medium, eg an elastic band, may be slipped around theoverlapping section of the shield. In the event that a rigid contact isnecessary, the overlapping shield section may be metal-bonded to thefrustoconical section.

Up to this point, the radiant heat barrier component of the compositemulti-layered insulation and the highly conductive metal shields havebeen described as two separate elements of the instant container. In oneembodiment, they may be the same element, as for example when aluminumor copper ribbon is wrapped in an orbital manner around the innervessel. In this construction, at least some of the ribbons overlap thelarge lower end of the frusto-conical section to achieve the necessarysolid path for heat conduction.

Referring now to the drawings and FIG. 1, a doublewalled, low boilingliquefied gas container is illustrated. Inner vessel 11 storing the lowboiling liquefied gas, e.g. liquid helium, is surrounded by outer shell13 with vacuum space 14 therebetween. The inner vessel 11 is supportedby neck tube 15 also serving as the previously defined evaporation gasconduit. Disposed within the vacuum space 14 is the compositemulti-layered insulation 15a, which may also serve to stabilize innervessel 11 against lateral movement or side-sway. Multiple heatconductive shields 16 extend concentrically around inner vessel 11 atintervals across the vacuum space 14 and are separated by layers ofcomposite-layered insulation 15a. 1

Frusto-conical sections 17 are concentrically aligned around conduit 15,spaced along the conduit length, and positioned with their small endsfrictionally bearing against the outer surface of conduit 15. Shieldedge 18 overlaps and is supported by the large end of section 17 forsolid conduction.

It has been found that the frusto-conical sections 17 may beintermittently snapped around evaporation gas conduit 15 during theinsulation wrapping operation without stopping the wrapping machine.This eliminates one important limitation of the previously describedmetal bonded disk construction.

'In one series of tests, double-walled liquefied gas containers of literliquid capacity were orbital wrapped with a composite insulation ofaluminum foil ribbon and glass fiber strips,.with and without thefrusto-conical sections. These sections were of the type illustrated inFIGS. 1 and 2, formed from -inch aluminum sheeting with a60-degreevertex angle and snapped on at equal intervals between 80 turnsof the composite insulation. To bring the aluminum ribbons in intimatephysical contact with the frusto-conical sections, the former wasaligned under the glass ribbon and over substantially the entire outersurface of the sections. It should be noted that in these containers,the same aluminum ribbon served as the radiation barrier component ofthe insulation, and the heat conductive shields. The width of the vacuumspace was 0.75 inch, and one container had only a single frusto-conicalsection placed midway through the composite insulation.

The normal evaporation rates of these containers were tested with bothliquid nitrogen and liquid hydrogen, and the following results wereobtained:

It is apparent from these tests that the insulation performance of thecontainers was improved at least 25% by the use of frusto-conicalsections to provide multishielded construction at the negligible expenseof a few simple aluminum stampings and no increase in labor time.

The invention was also successfully demonstrated in the construction ofa substantially larger container having 150 liter liquid capacity.Whereas the previously described 25 liter container is 18 inches longand has a 13.8 inch diameter (L/D ratio of 1.3), the larger 150 litercontainer is 44 inches long, 17 inches in diameter and has an L/D ratioof 2.59. The cone section used in the larger containers is shown in FIG.3, and is formed from 0.022-inch thick (16 oz./sq. ft.) electrolytictough pitch copper. The geometry of the container required a rather flatcone having a vertex angle of 140 degrees. Due to the large vertexangle, the frusto-conical section 117 did not inherently possess thenecessary elasticity to be snapped over the conduit. The are of contactbetween the section and the conduit would have been 270 de grees, thesame as the successful FIG. 2 frusto-conical section. To remedy thissituation, the section 117 was cut across most of its diameter leavingonly a small segment to hold the two semi-circular portions together(see FIG. 3). This feature provided an arc of contact of nearly 360degrees and a firm grip on the conduit. It required, however, the use ofa retaining ringv20 which is pressed into groove 21 around the small endof frusto-conical section 117 by means of clamp 22 (see FIG. 4). In thismanner, an excellent frictional contact is maintained betweenevaporation conduit 15 and frust-o-conical section 117, thereby insuringelfective heat transfer by solid conduction.

The large 150 liter container was orbital wrapped with a compositeinsulation of 3-inch wide aluminum foil ribbons and 3 /2-inch wide glassfiber paper ribbons to a density of 64 layers/inch vacuum space crosssection. F-our conductive metal shields were wrapped at intervals duringthe composite insulation wrapping, the shield material being tough pitchcopper ribbon 3 inches wide and 0.0007 inch thick /2 oz. per sq. ft).Each shield consisted of four turns of the orbital machine area whichcorresponds to 1.6 layers.

The assembly of a 150 liter liquid heliumacontainer using the previouslydescribed disks and a soft-solder joint to the evaporation conduitrequired about 15 manhours. Part of this time may be attributed to aspiral wrap. ping procedure whereby sheets of aluminum foil and glassfiber paper were employed and the composite insulation ends werelaboriously folded over each other one-'by-one. However, use of thepreviously described frusto-conical sections along with orbital wrappingreduced the required labor time by to 3 man-hours. Again, it was notnecessary to stop the wrapping machine to snap on the frusto-conicalsections. This remarkable savings in labor was obtained without s ininsulating eificiency, as the normal evaporation loss rate wassubstantially the same for the soft solder-disk arrangement and theclamped frusto-conical section construction.

In the interest of simplicity, the composite multilayered insulation 15ahas been shown schematically in FIG. 1. FIG. 5 illustrates one suitableform of this insulation in greater detail, and comprises a low heatconductive fibrous material 23 such as glass paper arranged inalternating layers with thin reflecting shields 24 for diminishing thetransfer of heat by radiation. The individual fibers of the glass paperlayers are preferably oriented substantailly parallel to the reflectingshields 24 and substantially erpendicular to the direction of heatinleak across the vacuum space between the outer casing and innervessel.

It has been previously stated that the composite multilayered insulationand highly conductive metal shield may be wrapped around the innervessel either in a spiral fashion or in an orbital manner. In eithercase the frustoconical sections are snapped onto the evaporation conduitand over the insulation layers after a desired number of insulationlayers have been formed. If the conductive shield is a separate element,it may then be wrapped around the vessel so as to overlap and lieagainst the installed frusto-conical section. Additional layers of thecomposite insulation are then wrapped around the inner vessel, over thefrusto-conical section and the metal shield (if separate), and thesequence is repeated until the desired number of composite insulationlayers-frustoconical sections-metal conductive shields have beeninstalled.

The orbital wrapping method is preferred for containers small enough tobe rotated about a vertical axis, i.e. up to about 12 feet long, andwill be briefly described hereinafter. A detailed description of orbitalwrapping is found in copending application S.N. 128,166 filed July 31,1961, now abandoned, of which the present application is acontinuation-in-part. In a broad sense, orbital wrapping comprises thesteps of providing at least two composite strips of the insulation, e.g.fibrous sheeting underlayer and metal foil, on opposite sides of thevessel and securing an end of each composite strip to the vesselsurface. The vessel is suspended vertically and rotated around its axis.The composite insulation strips are simultaneously orbited around therotating vessel in a plane which cuts the axis of the vessel at an angle0. In this manner, the strips are continuously delivered to the vesselfrom the top to the bottom thereof forming a continuous insulation matof crisscrossing strips.

The orbital wrapping sequence is illustrated in FIGS. 6 and 7 and willbe described in conjunction with the previously discussed ISO-literhelium container.

Inner vessel 11 is attached to the vertically aligned shaft 30 by meansof expansion mandrel (not shown) inserted into the evaporationconduit-neck tube 32 of vessel 11, and secured by a lock nut 31. Shaft30 in turn is connected to a suitable drive (not shown) so as to rotatethe vessel 11 about its axis. The drive may consist of any type of motorand speed reducing gears necessary to obtain the desired rotating speedof the vessel.

To orbital Wrap the ISO-liter vessel 11 having a length/ diameter ratioof 2.511, it was found necessary to orbit four systems of compositeinsulation ribbons (8 rolls altogetherfi. The four rotatable fibroussheeting rolls 33a-33d, and the corresponding four rotatable metal foilrolls 34a-34d are attached to four arms of the planetary support 35through respective shafts so as to be orbitable about the verticallyrotatable vessel 11. The roll rotation speed is determined by the speedof rotation of support 35. This speed was about 10 r.p.m. in the case ofrelatively long vessel 11, whereas in the case of the small spherical 25liter containers a higher rotational speed of about 30 r..p.m. was foundsatisfactory. Each pair of fibrous sheeting rolls 33a-33d and metal foilrolls 33a- 34d are adjacently positioned at 90-degree intervals so thatcomposite layers of fibrous sheeting underlayer and metal foils from thefour pairs of rolls are simultaneously applied on opposite sides of therotating container.

In a manner similar to the vessel 11 rotating means, planetary support35 having four motions arms is driven through a shaft by drive meanswhich, for example, may consist of a suitable motor and speed reducingmeans. The speed of planetary support 35 has a maximum value which isdetermined experimentally by the breaking load of the metal foil strip.

Having once determined the speed of planetary support 35, the speed ofthe vessel 11 is synchronized in a certain relationship to the speed ofsupport 35. This relationship depends upon the angle 0 between the planeof the orbiting rolls and the vertical axis of the vessel, the anglebetween the wrapping strip and the axis of the vessel, and the diameterof the vessel D If these factors are not properly determined, theinsulation strips form excessive wrinkles in those areas where there isa transition from one surface to another. These wrinkles will pile upthus forming a loose insulation mat with improper density.

For non-spherical vessels, e.g. cylindrical, the angle 0 between theplane of the orbit and the axis of the vessel is dependent upon thelength of the vessel, the diameter of the vessel neck tube-evaporationconduit, and the width of the strip. The relationship may be expressedmathematically as follows:

tan 9 wherein D =diameter of the vessel neck tube, L=length of thevessel, and w=width of the metal foil strip.

The angle that the applied composite wrapping strip makes with thevertical axis of the vessel results from the change of one surface toanother and is dependent upon the diameter of the vessel, the diameterof the vessel neck tube, and the width of the strip. Expressedmathematically:

wherein D =diameter of the vessel, D =diameter of the vessel neck tube,and w=width of the metal foil strip.

For a spherical vessel, these angles are equal since the surface of asphere is uniform. The magnitude of the orbiting angle for a sphericalvessel in degrees i expressed by the formula:

in which L=length of the vessel, D =diameter of the vessel, and theangles 1) and 0 are the wrapping and orbital angles respectively. Thisdisplacement is necessary in order that the wrapped composite strips ofinsulation be wound adjacent to each other onto the vessel and aswrinkle-free as possible to minimize the insulation pile up.

In wrapping the ISO-liter cylindrical vessel, the abovedefined angleswere as follows:

0:6 degrees (approximately) =16 degrees (approximately) :54 degrees(approximately) The wrapping of vessel 11 was initiated by insulatingribbons of 3-inch wide aluminum foil 36 and 3 /2-inch wide glass paper37 from the rolls to form a first section of 28 turns, corresponding to12 layers.

Since the radial force component of a ribbon wrapped in an almost axial.plane around a long cylindrical vessel is extremely small, thecomposite insulation cannot be wrapped to the desired density at thecylindrical portion,

but remains rather loose. In order to overcome this problem and have theinsulation compressed to the desired density of 60-70 layers per inch, a2 /2-inch wide woven glass fiber ribbon (not illustrated) washand-wrapped helically around the cylindrical portion of the vessel.This procedure was repeated at the end of each of the five sections.

On completion of each of the composite-layered insulating sections, acopper conductive shield was orbital wrapped. The 3-inch wide,0.0007-inch thick copper ribbon was positioned as rolls on the spindlespreviously used for the metal foil rolls 34a-34d. The rolls were orbitedin the previously described manner, each complete shield consisting offour strips 37 applied by four turns of the rotatable frame 35, whichcorresponds to 1.6 layers. The sequence of shield wrapping isillustrated in FIG. 7. After two turns of planetary support 35, themachine was stopped and a frusto-conical section 117 (see FIG. 3) wasattached to neck tube 32 by retaining ring 20. By this procedure, thecomposite insulation was slightly compressed by the inner, under surfaceof the frusto-conical section 117, since there is a natural build-up ofthe insulation at the polar area of the vessel. This slight compressionof the composite insulation provided a good thermal contact with thethermal shield 37. Without breaking the copper ribbons, the remainder ofthe copper ribbons (two turns of the orbital frame) was wrapped on topof the frusto-conical section 117, thus providing an excellent heattransfer path across the sections outer surface to the shield 37. Forexample, the total contact area between the shield 37 and frustoconicalsection 117 is on the order of 35 square inches. In marked contrast, thesoft soldered contact area of a spiral wrapped shield to a copper diskconcentrically positioned around the neck tube of a ISO-litercylindrical vessel as described in the previously described copendingapplication to Paivanas et al. is only about 3.5 sq. in.

The following table is a summary of the complete insulation constructionusing the orbital wrap method:

Section Turns Per Section Number Finished Number of Layers O.D., inchesI 28 insulation 12 13 25 4 conductive metal shield- 1. 6 II 30insulation 12. 4 18, 80

4 conductive metal shield. l. 6 III 32 insulation 12. 8 19. 35

4 conductive metal shield. 1. 6 1V 34 insulation 13. 2 19. 76

4 conductive metal shield. 1. 6 V. 36 insulation 13. 8

Total--- 160 64 20.

Although preferred embodiments of the invention have been described indetail, it is contemplated that modifications may be made by the art,all within the spirit and scope of the invention.

For example, the invention has been specifically described withreference to double-walled liquefied gas containers having verticallyaligned longitudinal axes. The longitudinal axis may also behorizontal-often a more desirable orientation for very large containers.Such large containers may need load rod support members in addition tothe previously described neck tube-gas evaporation conduit supportmember. One embodiment of this invention illustrated in FIG.. 8contemplates the use of frustoconical sections concentrically alignedaround these loadrod members with the large end of these sectionsthermally connected to the edge of a heat conductive shield.

Referring more specifically to FIG. 8, inner vessel 11 is supported andstabilized Within outer casing 13 by load rod members 40 constructed ofrelatively low heat conductive material, e.g. stainless steel. Load rods40 may be positioned at opposite ends of the container one end of eachrod bearing against and attached to inner vessel 11 while the other endbears against outer casing 13. Frusto-conical sections 41 formed of heatconductive metal are concentrically aligned around each load rod withinvacuum space 14 filled with composite multi-layered insulation 15a. Thesmall end of each frusto-conical section 41 is positioned with its smallend frictionally bean'ng against the outer surface of the load rod 40.If multiple frusto-conical sections are employed, they are spaced alongthe length of load rod 40.

At least one and preferably multiple highly conductive metal shields 16are disposed in the vacuum space 14 and surround inner vessel 11.Shields 16 are also contiguously associated on both sides with compositemulti-layered insulation 15a. The edge 18 of each shield adjacent to aparticular frusto-conical section 41 surrounding load rod 40 ispositioned in thermal contact with the'section large end, and the smallend of the same section is aligned and positioned in thermal contactwith load rod 40 so that the shield edge and conical sectiontemperatures are higher than the temperatures they would assume absentthe thermal contact. In this manner, the heat inleak conducted along thelength of load rods 40 is diverted through conical sections 41 andthermally associated shields 16 to the evaporation gas dischargedthrough conduit 15. That is, another edge of certain heat conductiveshields 16 is thermally associated with a selected frusto-conicalsection surrounding and frictionally bearing against evaporation gasconduit 15 in the previously described manner.

The outer end of evaporation gas conduit 15 preferably is associatedwith conventional pressure relief devices, i.e. relief valve 42 andbursting disk 43, if it is desired to maintain the liquefied gas ininner vessel 11 at above atmospheric pressure. Control valve 44 is alsoprovided in evaporation conduit 15.

What is claimed is:

1. A double-walled liquefied gas container comprising an inner storagevessel and an outer shell being arranged and constructed with a vacuumspace therebetween; an evaporation gas conduit between said inner vesseland said outer shell for transporting such gas from the container andhaving a temperature gradient across said vacuum space; a compositemulti-layered insulation disposed within such space comprising multiplelayers of precompacted paper ribbon and aluminum foil ribbon beingorbital wrapped crisscrossly in overlaying relation around said innervessel; multiple fru-sto-conical sections formed of aluminium sheetingof 0.02 to 0.0 4 inch thickness being concentrically aligned around saidevaporation conduit within said vacuum space, positioned with theirsmall ends frictionally bearing against the outer surface of the conduitfor thermal contact therebetween and longitudinally spaced along theconduit outer surface, at least some of the orbital wrapped aluminumribbons overlapping and contiguously thermally contacting the large endsof respective frusto-conical sections as heat conductive shields, theshields and frusto-conical section large ends as well as the sectionsmall ends and conduit outer surface being aligned with respect to thevacuum space width and thermally contacted so that the shield andfrusto-conical sections are at temperatures lower than the temperaturesthey would assume absent the contacts.

2. A double-walled liquefied gas container comprising an inner storagevessel and an outer shell being arranged and constructed with a vacuumspace therebetween; an evaporation gas conduit between said inner vesseland said outer shell for transporting such gas from the container andhaving a temperature gradient across said vacuum space; a compositemulti-layered insulation disposed within such space comprising multiplelayers of precompacted paper ribbon and aluminum foil ribbon beingorbital wrapped crisscrossly in overlaying relation around said innervessel; multiple frusto-conical sections formed of aluminum sheeting of0.02 to 0.04 inch thickness being concentrically aligned around saidevaporation gas conduit within said vacuum space, positioned with theirsmall ends frictionally bearing against the outer surface of the conduitfor thermal contact therebetween and longitudinally spaced along theconduit outer surface and copper foil ribbon orbital wrapped around saidinner vessel between and contiguously associated with adjacent layers ofsaid composite multi-layered insulation, said copper foil ribbon beingpositioned so as to overlap and contiguously thermally contact the largeends of respective frustoconical sections as heat conductive shields,the shields and frusto-conical section large ends as well as the sectionsmall ends and outer surface being aligned with respect to the vacuumspace width and thermally contacted so that the shield andfrusto-conical sections are at temperatures lower than the temperaturesthey would assume absent the contacts.

3. A double-walled liquefied gas container comprising an inner storagevessel and an outer shell being arranged and constructed with a vacuumspace therebetween', an evaporation conduit between said inner vesseland said outer shell for transporting such gas from the container andhaving a temperature gradient across said vacuum space; a frusto-conicalsection formed of heat conductive metal being concentrically alignedaround said evaporation conduit within said vacuum space and positionedwith its small end frictionally bearing against the outer surface of theconduit for thermal contact therebetween; a composite multilayeredinsulation disposed within such space comprising ribbons of a low heatconductive non-metallic component and a metallic reflective componentbeing wrapped criss-crossly in overlaying relation around said innervessel, at least some of said ribbons being positioned with edgesoverlapping the outer surface of the large end of said frusto-conicalsection as a highly conductive metal shield, the shield edge andfrusto-conical section large end as well as the section small end andthe conduit outer surface being aligned with respect to the vacuum spacewidth and thermally contacted so that the shield edge and frusto-conicalsection are at temperatures lower than the temperatures they wouldassume absent the contacts.

4. A double Walled container as claimed in claim 3 wherein saidcomposite multilayered insulation is orbital wrapped criss-crossly inoverlaying relation around said inner vessel.

5. A double walled liquefied gas container as claimed in claim 3including load-rod members provided in said vacuum space and positionedwith opposite ends bearing against said inner vessel and said outercasing so as to support and stabilize said inner vessel; multiplefrustoconical sections formed of heat conductive metal beingconcentrically aligned around said load-rod members and positioned withtheir small ends frictionally bearing against the surface of saidmembers for thermal contact therebetween and longitudinally spaced alongsaid surface; multiple conductive shields disposed in said vacuum spaceand surrounding said inner vessel in spaced relation to each other,another edge of said shield contigu'ously thermally contacting the largeends of respective frusto-conical sections, said another shield edge andmatching frusto-conical section large ends as well as the section smallend and load-rod members surface being aligned with respect to thevacuum space width and thermally contacted so that the shield edge andconical section temperatures are lower than the temperatures they wouldassume absent the thermal contact.

References Cited Improve the Vacuum Insulation of the Dewar Flask, TVF,vol. 29, 1958, p. 151-160 (Teknisk-Vetenskaplig Forsknng).

THERON E. CONDON, Primary Examiner.

JAMES R. GARRETT, GEORGE E. LOWRANCE,

Examiners. R. A. JENSEN, Assistant Examiner.

1. A DOUBLE-WALLED LIQUEFIED GAS CONTAINER COMPRISING AN INNER STORAGEVESSEL AND AN OUTER SHELL BEING ARRANGED AND CONSTRUCTED WITH A VACUUMSPACE THEREBETWEEN; AN EVAPORATION GAS CONDUIT BETWEEN SAID INNER VESSELAND SAID OUTER SHELL FOR TRANSPORTING SUCH GAS FROM THE CONTAINER ANDHAVING A TEMPERATURE GRADIENT ACROSS SAID VACUUM SPACE; A COMPOSITEMULTI-LAYERED INSULATION DISPOSED WITHIN SUCH SPACE COMPRISING MULTIPLELAYERS OF PRECOMPACTED PAPER RIBBON AND ALUMINUM FOIL RIBBON BEINGORBITAL WRAPPED CRISSCROSSLY IN OVERLYING RELATION AROUND SAID INNERVESSEL; MULTIPLE FRUSTO-CONICAL SECTIONS FORMED OF ALUMINUM SHEETING OF0.02 TO 0.04 INCH THICKNESS BEING CONCENTRICALLY ALIGNED AROUND SAIDEVAPORATION CONDUIT WITHIN SAID VACUUM SPACE, POSITIONED WITH THEIRSMALL ENDS FRICTIONALLY BEARING AGAINST THE OUTER SURFACE OF THE CONDUITFOR THERMAL CONTACT THEREBETWEEN AND LONGUITDINALLY SPACED ALONG THECONDUIT OUTER SURFACE, AT LEAST SOME OF THE ORBITAL WRAPPED ALUMINUMRIBBONS OVERLAPPING AND CONTIGUOUSLY THERMALLY CONTACTING THE LARGE ENDSOF RESPECTIVE FRUSTO-CONICAL SECTIONS AS HEAT CONDUCTIVE SHIELDS, THESHIELDS AND FRUSTO-CONICAL SECTION LARGE ENDS AS WELL AS THE SECTIONSMALL ENDS AND CONDUIT OUTER SURFACE BEING ALIGNED WITH RESPECT TO THEVACUUM SPACE WIDTH AND THERMALLY CONTACTED SO THAT THE SHIELD ANDFRUSTO-CONICAL SECTIONS ARE AT TEMPERATURES LOWER THAN THE TEMPERATURESTHEY WOULD ASSUME ABSENT THE CONTACTS.